20 ms·

Physics Without Probability (2015) [video]

56 points by sytelus 6y ago

f430 6y ago
This is absolutely fascinating. This could be something quite ground breaking.
marta_morena_9 6y ago
To speed things up: http://constructortheory.org/what-is-constructor-theory/ http://constructortheory.org/what-is-constructor-theory/ This is what the video talks about. I don't like this video much. It's tedious and lengthly. Probably no reasonable human being would assume that Quantum Mechanic as we know it is the "holy grail" of physics. We came up with it within 100 years. Can we explain everything? Of course not. To me, the fact that we have the uncertainty principle and schroedingers cat already prove that we basically built our understanding of physics on the premise that we can never understand it. We were basically throwing the towel and saying "yeah this is it". Advances are made through measurement and verification. How do you understand something that you can't measure, because the measurement changes the system? It was pretty obvious to me when I studied physics that this is 100% not how the world works. It's a model, like everything else. In the model of quantum mechanics, which undoubtedly is one of the most impressive human achievements nonetheless, we have essentially complete uncertainty on the quantum scale. We can not peek beyond it and it doesn't give us any insights into how to peek beyond it. It is, in a way, the end of the line. And like any end of the line in science, it needs a radically different thought or model, to overcome. I always found it amusing how physicists, who really should know better, actually believe that quantum mechanics is how the world works and that this is it. I always was with Einstein in rejecting Quantum Theory. It's a nice model. But that's really all it is. A model. This is not how the world works and we have come to see its limitations. We need something better if we ever want to leave our solar system and colonize space. Even Einstein fell into the trap of thinking that Quantum Mechanics is more than a model. "God does not throw a dice". Probably he does not, but it's the best approximation we could come up with. He should have refuted it and looked for something better instead. Who knows where we would be now.
- aeternum 6y ago
  This idea seems similar to Wolfram's somewhat new hypergraph + rule idea: https://writings.stephenwolfram.com/2020/04/finally-we-may-have-a-path-to-the-fundamental-theory-of-physics-and-its-beautiful/ https://writings.stephenwolfram.com/2020/04/finally-we-may-h...
  - quiescant_dodo 6y ago
    This is a fascinating read. Thanks for sharing.
- warbaker 6y ago
  You're familiar with Bell's Theorem, yes? QM puts significant constraints on any physical theory that might underlie it.
- mrmonkeyman 6y ago
  He tried. Many people tried.
- wruza 6y ago
  The uncertainty is not exclusive to QM and is a property of any ‘wavy’ system, it seems. It is inherent. Here is the example: https://m.youtube.com/watch?v=MBnnXbOM5S4 https://m.youtube.com/watch?v=MBnnXbOM5S4 — if you want to defeat QM, attack its wave-part. It would be nice to have much better (deterministic, measurable) physics, but some properties just emerge from a fundamental level and you can’t do much about it (monster group etc). Nature and maths don’t care about our confusion and convenience. >should have refuted it and looked for something better instead Afaik, the time when theories were driven by ideas is over. Today it’s petabytes of data that you can’t really argue with over a mailbox, only discuss. (I’m just a layman physicist with deep interest, but shallow understanding, so please don’t quote me on any of this)
- simiones 6y ago
  Honestly, seeing the high-level requirements for what constructor theory defines as Possible / Impossible, I mostly expect that it will have to conclude that many of the transformations that happen in QM are Impossible (a constructor can't be conceived that could achieve those tasks with arbitrary precision and reliability). Related to your observations, I believe you are absolutely right in that it's likely we've sort of reached the end of the road in exploring beyond the quantum scale with the current approach. I do believe there are some dangling threads that can be pulled to help guide some other directions - such as the measurement problem and the no-communication theorem. I also have some hope that computer theory may be able to shed some light - at the moment, we have a clear distinction between quantum algorithms and classical algorithms, but we don't know if they are fundamentally different or not. A discovery of how to efficiently compute quantum algorithms on classical computers (i.e. BQP = P or at least BQP = NP) would likely be a major insight into QM itself. Conversely, proof that quantum computers are fundamentally different from classical computers would also hopefully show WHY/HOW they are different and help in this area. Alternatively, if it turns out that quantum computers are in fact not physically realizable or require exponential memory or energy would essentially prove that physical reality does not obey some of the properties that make quantum computers (apparently) more powerful than classical computers.
myWindoonn 6y ago
Knowing a bit of maths, I'm having trouble understanding how this isn't just categorical logic. They say that the laws of physics should be expressible in terms of statements about which physical transformations are possible or impossible, and why. In categorical logic, laws are expressible in terms of statements about which morphisms exist or would be contradictory/absurd to exist, and include proofs. What's the difference? I read through a couple of their preprints but didn't find much concrete material, just a lot of complaints about existing theoretical physics traditions.
roenxi 6y ago
It is an interesting approach to physics and good luck to them. But the video isn't promising. The reason a physicist models a thing as a random variable is because they don't know of a way to distinguish the thing from a random variable. Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. The important part isn't conceiving of something as deterministic. That is easy to do. Proving it experimentally will be the hard part. There is nothing to report until there is an experiment that people can hold up saying "see! we found it! This part is deterministic not probabilistic!".
- scotty79 6y ago
  > Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. Especially given that sum of billion random variables is determined and pretty precise value.
  - YeGoblynQueenne 6y ago
    Well, one's horoscope is also a set of "determined and pretty precise" values but that's not to say that we have learned anything useful from looking at a person's horoscope, except from what can be informed by a belief that it influences a person's behaviour. That is to say, that the value of a variable can be precisely known doesn't say anything about the utility of knowing that value. Accordingly, the talk in the linked video is not arguing that the values of random variables cannot be determined with precision, rather that doing so is not sufficiently informative for the purposes of understanding physical reality.
- thingification 6y ago
  From memory of listening to this a few times some time ago (caveat: I certainly didn't study the content of this video carefully, but I do understand some significant context of his work as he sees it reasonably well I think): Deutsch here isn't trying to modify quantum mechanics, he's trying to "interpret" it. He wouldn't use the term "interpret" of course, for excellent and fascinating reasons that I can't quickly cram into an HN post, but you can find them in his book The Beginning of Infinity (I was convinced about this area of what he says in the book, not about everything else he says there -- there's a LOT of stuff in there!). By the way, I don't know whether or not you meant to imply that Deutsch is not a physicist, but he is -- and well known for his work on the fundamentals of quantum physics.
contravariant 6y ago
I think they're begging the question a bit when it comes to thermodynamics. In their video on http://constructortheory.org/what-is-constructor-theory/ http://constructortheory.org/what-is-constructor-theory/ they simply claim that no constructor exists that can turn a cooked egg into a raw egg and that allows their theory to reason about thermodynamics. Now presumably this is meant to be about entropy and not merely the amount of energy. However given the exact right amount of energy it is possible for a constructor to 'uncook' an egg, it's just that this constructor will work only for exactly that egg at exactly that time. The resolution is that you're extremely unlikely to pick the right constructor but then we're back to probability again. In fact anything the recovers the laws of thermodynamics simply ends up recovering probability theory as the laws of thermodynamics are inherently probabilistic.
- quirky_mind 6y ago
  Looks like someone reinvented operators. Or am I missing something here?
  - contravariant 6y ago
    Well I guess they're assuming the operators are more physical than theoretical and they should conserve things (so I think they're limited to hermitian operators). But yeah that sounds about right. Not that I mind that they're looking for a different foundation but you can't just gloss over the problem of explaining statistical physics without statistics...
- Chinjut 6y ago
  Their definition of "constructor" is as something that will perform a task reliably (whose meaning they define as including repeatably) for any choice of input with the specified attribute. If you can't come up with some reliable repeatable way of turning any cooked egg into a raw egg, then you don't have the thing they call a "constructor" for turning cooked eggs into raw eggs.
markus_zhang 6y ago
Watched 30 minutes and pretty much didn't get what he wanted to express, which is pretty fine because I'm not well versed in the art of Physics. Just one thing about probability. My theory is that we use probability because we don't really understand the true "why" of things, or we don't know them. For example, we use probabiliy to guide us when playing poker, but that's because we don't know the cards. Whence we know the cards there is no need for probability. But again, he is probably not speaking about the same "level" of things. I wish I knew more Physics.
- jvanderbot 6y ago
  All models are wrong, but some are useful. I'm with you, we use probability to wave away effects we don't understand or cannot measure. There's a flat rate probability that each of us has cancer right now, when perfect knowledge of our bodies could answer the question precisely. Each doctor exam we have reduces or increases that probability until we subjectively understand it's time to sample a point of the body and know for certain. The local sample is related to the larger system, and the hidden variable (cancer or not). The local sample at the time of capture has a probability of being malignant. We measure directly and back propagate the results to the system. But, unintuitively, there's been some famous results that seemingly preclude a deterministic explanation of quantum mechanics. See: - https://en.wikipedia.org/wiki/Hidden-variable_theory https://en.wikipedia.org/wiki/Hidden-variable_theory - https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem
lisper 6y ago
I did a deep dive into Deutsch's game-theoretic interpretation of QM (which he talks about mid-way through the talk) a while back. This is the result: http://blog.rongarret.info/2019/07/the-trouble-with-many-worlds.html http://blog.rongarret.info/2019/07/the-trouble-with-many-wor...

56 points by sytelus 6y ago

f430 6y ago

This is absolutely fascinating. This could be something quite ground breaking.

To speed things up: http://constructortheory.org/what-is-constructor-theory/ http://constructortheory.org/what-is-constructor-theory/ This is what the video talks about. I don't like this video much. It's tedious and lengthly. Probably no reasonable human being would assume that Quantum Mechanic as we know it is the "holy grail" of physics. We came up with it within 100 years. Can we explain everything? Of course not. To me, the fact that we have the uncertainty principle and schroedingers cat already prove that we basically built our understanding of physics on the premise that we can never understand it. We were basically throwing the towel and saying "yeah this is it". Advances are made through measurement and verification. How do you understand something that you can't measure, because the measurement changes the system? It was pretty obvious to me when I studied physics that this is 100% not how the world works. It's a model, like everything else. In the model of quantum mechanics, which undoubtedly is one of the most impressive human achievements nonetheless, we have essentially complete uncertainty on the quantum scale. We can not peek beyond it and it doesn't give us any insights into how to peek beyond it. It is, in a way, the end of the line. And like any end of the line in science, it needs a radically different thought or model, to overcome. I always found it amusing how physicists, who really should know better, actually believe that quantum mechanics is how the world works and that this is it. I always was with Einstein in rejecting Quantum Theory. It's a nice model. But that's really all it is. A model. This is not how the world works and we have come to see its limitations. We need something better if we ever want to leave our solar system and colonize space. Even Einstein fell into the trap of thinking that Quantum Mechanics is more than a model. "God does not throw a dice". Probably he does not, but it's the best approximation we could come up with. He should have refuted it and looked for something better instead. Who knows where we would be now.

aeternum 6y ago
This idea seems similar to Wolfram's somewhat new hypergraph + rule idea: https://writings.stephenwolfram.com/2020/04/finally-we-may-have-a-path-to-the-fundamental-theory-of-physics-and-its-beautiful/ https://writings.stephenwolfram.com/2020/04/finally-we-may-h...
- quiescant_dodo 6y ago
  This is a fascinating read. Thanks for sharing.
warbaker 6y ago
You're familiar with Bell's Theorem, yes? QM puts significant constraints on any physical theory that might underlie it.
mrmonkeyman 6y ago
He tried. Many people tried.
wruza 6y ago
The uncertainty is not exclusive to QM and is a property of any ‘wavy’ system, it seems. It is inherent. Here is the example: https://m.youtube.com/watch?v=MBnnXbOM5S4 https://m.youtube.com/watch?v=MBnnXbOM5S4 — if you want to defeat QM, attack its wave-part. It would be nice to have much better (deterministic, measurable) physics, but some properties just emerge from a fundamental level and you can’t do much about it (monster group etc). Nature and maths don’t care about our confusion and convenience. >should have refuted it and looked for something better instead Afaik, the time when theories were driven by ideas is over. Today it’s petabytes of data that you can’t really argue with over a mailbox, only discuss. (I’m just a layman physicist with deep interest, but shallow understanding, so please don’t quote me on any of this)
simiones 6y ago
Honestly, seeing the high-level requirements for what constructor theory defines as Possible / Impossible, I mostly expect that it will have to conclude that many of the transformations that happen in QM are Impossible (a constructor can't be conceived that could achieve those tasks with arbitrary precision and reliability). Related to your observations, I believe you are absolutely right in that it's likely we've sort of reached the end of the road in exploring beyond the quantum scale with the current approach. I do believe there are some dangling threads that can be pulled to help guide some other directions - such as the measurement problem and the no-communication theorem. I also have some hope that computer theory may be able to shed some light - at the moment, we have a clear distinction between quantum algorithms and classical algorithms, but we don't know if they are fundamentally different or not. A discovery of how to efficiently compute quantum algorithms on classical computers (i.e. BQP = P or at least BQP = NP) would likely be a major insight into QM itself. Conversely, proof that quantum computers are fundamentally different from classical computers would also hopefully show WHY/HOW they are different and help in this area. Alternatively, if it turns out that quantum computers are in fact not physically realizable or require exponential memory or energy would essentially prove that physical reality does not obey some of the properties that make quantum computers (apparently) more powerful than classical computers.

myWindoonn 6y ago

Knowing a bit of maths, I'm having trouble understanding how this isn't just categorical logic. They say that the laws of physics should be expressible in terms of statements about which physical transformations are possible or impossible, and why. In categorical logic, laws are expressible in terms of statements about which morphisms exist or would be contradictory/absurd to exist, and include proofs. What's the difference? I read through a couple of their preprints but didn't find much concrete material, just a lot of complaints about existing theoretical physics traditions.

roenxi 6y ago

It is an interesting approach to physics and good luck to them. But the video isn't promising. The reason a physicist models a thing as a random variable is because they don't know of a way to distinguish the thing from a random variable. Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. The important part isn't conceiving of something as deterministic. That is easy to do. Proving it experimentally will be the hard part. There is nothing to report until there is an experiment that people can hold up saying "see! we found it! This part is deterministic not probabilistic!".

scotty79 6y ago
> Dr. Deutsch spent far too much time talking about the fact that at a high level there are a lot of things we are certain about. That is very weak evidence of what is happening at the quantum level. Especially given that sum of billion random variables is determined and pretty precise value.
- YeGoblynQueenne 6y ago
  Well, one's horoscope is also a set of "determined and pretty precise" values but that's not to say that we have learned anything useful from looking at a person's horoscope, except from what can be informed by a belief that it influences a person's behaviour. That is to say, that the value of a variable can be precisely known doesn't say anything about the utility of knowing that value. Accordingly, the talk in the linked video is not arguing that the values of random variables cannot be determined with precision, rather that doing so is not sufficiently informative for the purposes of understanding physical reality.
thingification 6y ago
From memory of listening to this a few times some time ago (caveat: I certainly didn't study the content of this video carefully, but I do understand some significant context of his work as he sees it reasonably well I think): Deutsch here isn't trying to modify quantum mechanics, he's trying to "interpret" it. He wouldn't use the term "interpret" of course, for excellent and fascinating reasons that I can't quickly cram into an HN post, but you can find them in his book The Beginning of Infinity (I was convinced about this area of what he says in the book, not about everything else he says there -- there's a LOT of stuff in there!). By the way, I don't know whether or not you meant to imply that Deutsch is not a physicist, but he is -- and well known for his work on the fundamentals of quantum physics.

contravariant 6y ago

I think they're begging the question a bit when it comes to thermodynamics. In their video on http://constructortheory.org/what-is-constructor-theory/ http://constructortheory.org/what-is-constructor-theory/ they simply claim that no constructor exists that can turn a cooked egg into a raw egg and that allows their theory to reason about thermodynamics. Now presumably this is meant to be about entropy and not merely the amount of energy. However given the exact right amount of energy it is possible for a constructor to 'uncook' an egg, it's just that this constructor will work only for exactly that egg at exactly that time. The resolution is that you're extremely unlikely to pick the right constructor but then we're back to probability again. In fact anything the recovers the laws of thermodynamics simply ends up recovering probability theory as the laws of thermodynamics are inherently probabilistic.

quirky_mind 6y ago
Looks like someone reinvented operators. Or am I missing something here?
- contravariant 6y ago
  Well I guess they're assuming the operators are more physical than theoretical and they should conserve things (so I think they're limited to hermitian operators). But yeah that sounds about right. Not that I mind that they're looking for a different foundation but you can't just gloss over the problem of explaining statistical physics without statistics...
Chinjut 6y ago
Their definition of "constructor" is as something that will perform a task reliably (whose meaning they define as including repeatably) for any choice of input with the specified attribute. If you can't come up with some reliable repeatable way of turning any cooked egg into a raw egg, then you don't have the thing they call a "constructor" for turning cooked eggs into raw eggs.

markus_zhang 6y ago

Watched 30 minutes and pretty much didn't get what he wanted to express, which is pretty fine because I'm not well versed in the art of Physics. Just one thing about probability. My theory is that we use probability because we don't really understand the true "why" of things, or we don't know them. For example, we use probabiliy to guide us when playing poker, but that's because we don't know the cards. Whence we know the cards there is no need for probability. But again, he is probably not speaking about the same "level" of things. I wish I knew more Physics.

jvanderbot 6y ago
All models are wrong, but some are useful. I'm with you, we use probability to wave away effects we don't understand or cannot measure. There's a flat rate probability that each of us has cancer right now, when perfect knowledge of our bodies could answer the question precisely. Each doctor exam we have reduces or increases that probability until we subjectively understand it's time to sample a point of the body and know for certain. The local sample is related to the larger system, and the hidden variable (cancer or not). The local sample at the time of capture has a probability of being malignant. We measure directly and back propagate the results to the system. But, unintuitively, there's been some famous results that seemingly preclude a deterministic explanation of quantum mechanics. See: - https://en.wikipedia.org/wiki/Hidden-variable_theory https://en.wikipedia.org/wiki/Hidden-variable_theory - https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem

lisper 6y ago

I did a deep dive into Deutsch's game-theoretic interpretation of QM (which he talks about mid-way through the talk) a while back. This is the result: http://blog.rongarret.info/2019/07/the-trouble-with-many-worlds.html http://blog.rongarret.info/2019/07/the-trouble-with-many-wor...